debugging a modern laptop ...

Greetings!

I'm trying to evaluate my options on debugging a recent laptop/notebook/table (and the Linux kernel on it of course) from early bootup to diagnostics when the machine has locked up ...

normally the first thing I would do is to attach a serial console to monitor the early bootup and have some way to send sysrq triggers ... but here is the first problem, the thing might not even have a serial port at all ...

most modern devices have at least one usb port, but as far as I could figure out via google, there is no support for console or similar over usb (serial or not) atm (please feel free to correct me here :)

after some research, I also found a quite antique project exploiting the ieee1394 DMA feature, called firescope and after some issues finding the latest version of the tool and of course getting a firewire cable, there seems to be some kind of interaction between the monitoring system and the device in question, but it seems that a few problems exist and I didn't manage to get any relevant information that way yet (please let me know if that is still maintained)

finally, ethernet and netconsole, which seems to work reasonably well, at least for the console logging part but requires at least a supported 'wired' ethernet interface and a few tricks to send commands to the device ... (but only partially suited or early bootup of course)

have I missed something?

what about bluetooth? (usually requires USB)
what about wireless? (probably quite problematic)

maybe a new kind of debug interface is needed in the near future?

any ideas and real world experiences are more than welcome ...

many thanks in advance,
Herbert

There is also USB debugport, but you need a quite expensive cable (~$100) for it. Usually it only works on one of the USB ports.

It works, but you need to enable it of course. The printk buffer hasn't changed for a long time.

The only problem often is that it doesn't support memory >4GB, however it turns out that some LSI chips support >4GB DMA and with those it works too.

-Andi

[email protected] -- Speaking for myself only.

There _is_ support for a USB console (see CONFIG_USB_SERIAL_CONSOLE). However it may not be useful for diagnosing problems during boot, because obviously the console won't operate until the USB stack is in place and running.

Alan Stern

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If you are lucky enough to have an ExpressCard slot on the notebook, then lots of eBay sellers offer "Oxford chipset" serial/parallel ports in ExpressCard format.

These provide "true" bus serial ports, which can be used as Linux consoles for low level kernel debugging, logs, panics, etc..

As a bonus, he parallel ports from the same chips can be used for homebrew JTAG adapters.

-ml